Electrical musical instrument



R. H. RANGER ELECTRICAL MUSICAL INSTRUMENT May 5, 1936.

Filed May 28, 1934 4 Sheets-Shut 1 INVENTOR R. H. RANGER BY Wf ATTORNEYSy 1935- v R. H. RANGER 2,039,659

ELECTRICAL MUSICAL INSTRUMENT Filed May 28; 1934 4 Sheets-Sheet 2 I i6.J

INVENTOR ATTORNEYS 4 Sheets-Sheet 3 Elf:

R. H. RANGE 1R ELECTRICAL MUSICAL INSTRUMENT Filed May 28, 1934 66 67 fU lll May 5, 1936.

INVENTOR R. H. RANGER B v M ATTORNEYS I 1&0 15-3 y 936. R. H. RANGER2,039,659

ELECTRICAL MUSICAL INSTRUMENT Fi-led May 28, 1934 4 Sheets-Sheet 4 m 143m5 m5 1 153 1 134 155 1 L156 LL13? 95? 4 ,96 'Q I I INVENTOR. R- H.RANGER A TTORNIEYS.

Patented May 5, 1936 srrss 17 Claims.

This invention relates to electrical musical systerms of the type inwhich musical tones are produced by means of electrical oscillations.

It is an object of the invention to provide an improved instrument ofthis type. Sound production in musical instruments by means ofelectrical oscillations is an old expedient and usually has involved thedrawbacks of high cost, prohibitive space requirements, mechanical orelectrical instability, high maintenance cost, high noise level, andmusical results which did not warrant many proposed electrical systems.'This invention provides an instrument with none of these drawbacks.

The present invention concerns a musical instrument involving the use ofphoto-electric or other light sensitive cells whose electrical output isinfluenced through the use of an interrupted light beam. In the pastinstruments have been devised in which rotating apertured discsinterrupted a light beam with a frequency corresponding to the pitch ofthe desired musical tone. One serious drawback to such a system was thatunless the openings were alined with extreme'accuracy disagreeablevariations in frequency, intensity, or both resulted from even minuteeccentricities in the mechanical construction. Another problem was tomaintain the speed of the apertured discs absolutely constant.

One object of the present invention is to provide an electrical musicalinstrument in which these difficulties are overcome. To this end Iemploy a vibrating element of. reliable frequency as a control elementfor the variable intensity of the light. As an illustrative. device anair driven reed oi the type commonly employed in reed organs will bedescribed. The invention, however,

is not limited to the use of an air-driven reed interrupter. Othervibrating devices may be used for light interrupters such aselectrically maintained reeds, strings, plates, or membranes. I

prefer the use of organ reeds as their cost is very low and theiroperation reliable.

Another object .of my invention is to provide an electrical musicalinstrument whose space requirements are low. In the instrument to bedisclosed only 72 vibrating reeds are needed to produce the desirednotes in -.a large number of tone colors through the musical pitchrange.- Many times this number of ordinary reeds or pipes would berequired to produce a corresponding numberoi notes and tone colors in apipe organ with a consequently larger space requirement.

Still another object is to provide an instru- (Ci. fi l-J) ment whoseaction shall be as nearly instantaneous as possible and permit no delaywhich the ear is capable of detecting. I provide a keyboard whichconveniently may be like that of a modern pipe organ console. Depressionof a key closes an electrical circuit which causes a lamp to be comeincandescent the emitted light of which is interrupted or given avarying intensity by the vibrating reed and then falls upon thesensitive surface of a photo-electric cell which converts the lightoscillations into electrical oscillations with subsequent electricalamplifiers and assc ciated sound projectors. A suificiently high voltage is applied to the filaments oi the lamps so that they become fullyincandescent immediate ly upon closing of their circuits by depressionoi the keys of the instrument. This gives an ac= tion tothe instrumentfar superior to that of the pipe organ; that is the length of timebetween depression of the key and. perception oi the correspondingacoustical phenomena is impercepti= tale in the case of my instrument,whereas this time interval for a pipe organ, esmcially for the longpipes whose air columns take time to be set into vibration, isconsiderable.

Another object is to provide a musical instru-= ment whose tone colormay be altered conven iently and through a wide range.

Still another object is to provide a musical in strument whose overalldynamic range may be. varied over a very wide range irrespective of tonecolor. For instance. the dynamic level of a flute tone color may bevaried from the threshold oi audibility to any level above this bysuitable. control of the electrical output of the amplifier.

The invention in a preferred form provides for the electrical productionof music through aplurality of elements each of which consists of thecombination of a keyed light beam whose shape may be varied withinpredetermined limits, an

air-driven reed whose mirror surface periodically deflects the shapedlight beam, a suitably positioned light slit upon which the shaped lightbeam is focused, a photo-electric cell whose sensitive surface isactivated by the light passing through the slit, a suitable amplifierto' strengthen the photo-celloutput, and sound projecting equipment toconvert the electrical energy delivered by the amplifier'intocorresponding acoustical energy.

Such an embodiment of the invention will be described, but while thisembodiment illustrates a preferred form it will nevertheless beunderstood that this description is merely illustrative members,

Fig. 4 is a view showing the light gate,

Fig. 5 is a view showing an alternative arrangement of elements of aunit for producing one note,

Fig. 6 is a detail view of the operating mechanism for adjusting thevalve members of the light valve shown in Fig. 2,

Fig. '7 is a view showing a plurality of note units actuating onephoto-electric cell,

Fig. 8 is a detail view showing an alternative form of light valvewherein a film of graded densities is substituted for the rotatablevalve members of the light valve shown in Fig. 2,

Fig. 9 is a detail sectional view taken on the line 9-9 of Fig. 8,

Fig. 10 is an electrical diagram showing the amplifiers between a seriesof photo-cells and a loud speaker,

Fig. 11 is an electrical diagram of a device for use in producing apercussion type of note,

Fig. 12 is an electrical diagram of anamplifier blocking arrangement,

Fig. 13 is a diagrammatic perspective view showing two reeds positionedside by side within the same wind chest,

Fig. 14 is a diagrammatic view illustrating a manner of using one reedfor producing the same note for two different manuals,

Fig. 15 is a diagrammatic view illustrating an arrangement wherein ashutter is provided for keying the notes,

Fig. 16 is an electrical diagram showing an arrangement whereby thecontent of each note is obtained from different reeds vibrating inharmonic relation.

In the musical instrument to be described for the purposes ofillustration, the arrangements for the several notes are similar. Thedescription of one set will suiiiciently illustrate the in vention. Eachnote is produced by light impinging upon a light sensitive cell, thelight being varied in accordance with frequencies corresponding to thefrequencies of the fundamental and overtones of the note to be produced.

The instrument is controlled from a console as usual and various stopsare provided for modifying the quality of the notes. Referring to Fig 1illustrating light control devices for two notes, lamps 5 are controlledby keys 8 at the console. The light from each lamp is directed along asuitable path to the light sensitive cell which conveniently may be aphoto-electric cell 1. Devices are interposed in the path of the lightbetween the lamp and the cell to cause a variation of the intensity ofthe light in accordance with the pattern of the fundamental and thedesired overtones of the note to be produced. In the arrangementillustrated, the light from each lamp 5 passes through a condenser 8, alight valve 9, an optical wedge or variable density film III, focusinglens II and is reflected by the mirror surface l2 of the reed H fromwhence it passes through light gate l5 to the cell 1. The reed I3 ismaintained in a state of continuous vibration at the natural frequencyof the reed during operation of the instrument by means of a suctionpump l6 which maintains suction in a chamber H extending beneath the rowof similar units, each unit being connected to the chamber ll as bypassages i8 and IS. The vibration of the reed serves to sweep the lightbeam across the light gate l5 and therefore by giving a suitable patternto the light beam, the intensity of light incident upon thephoto-electric cell 1 will vary in accordance with the desired pattern.To accomplish this result the lens II is adjusted to position to focusthe pattern of the light valve 9 in the plane of the light gate 15. Thelight valve as best shown in Fig. 2 is formed to provide threerectangular ports 20, 2|, 22 controlled by rotatably mounted valvemembers 23, 24, 25. The physical dimensions of the valve members will bedetermined by the amplitude of the reed vibration and the magnificationof the optical system. In the original construction of the instrumentthe dimensions of the respective valve members and of the valve portswill be fitted to provide for the desired intensities of the lightpassing therethrough. These valve members are shown as nearlyrectangular in cross-section and so shaped that when inthe positionshown in Fig. 2 they permit passage of .the maximum amount of light butas they are rotated from this position they close the ports more andmore until when turned at right angles to this position they entirelyclose the respective ports. suitably rounded at the corners so that theprofiles will be of a proper shape to pass light of a good wave patternas they turn. The particular shape of these valve members will bereadily understood from the perspective view of the member 25 shown inFig. 3.

Instead of a valve arrangement such as above described a type of valvemay be provided in which the light pattern, that is to say the variationof intensity of the light passed through the valve opening will becontrolled by variable density films. A suitable arrangement isillustrated in Figs. 8 and 9, wherein a variable density film isprovided, the density of the sections 20, 2|, 22' of the film from topto bottom varying in accordance with suitable wave patterns. The amountof light passed through the three sections may be varied by the openingand closing of shutters 25 which are shown as pivoted and rotatable topass more or less light. The intensity of the respective partials of thenote to be produced is therefore controlled by the movement of theseshutters.

The central valve member 24 of Fig. 2 is shown as of uniform taperthroughout its effective portion. During vibration of the reed, whichmovement is naturally of sine character, the different portions of thevalve member 24 will successively control the amount of light passingthrough the gate IS in such a manner that the variation in intensity atthe photo-electric cell 1 will be in accordance with the sine wavepattern and will correspond to the fundamental frequency of thevibrating reed l3.

The valve member 25 is arranged to admit light to the photo-electriccell varying in intensity in accordance with a sine wave pattern, but ata rate corresponding to the octave of the fundamental, that is thesecond partial of the note to be produced. The particular shape of thisvalve memher is readily plotted by bearing in mind the natural sine wavemovement'of the reed l3 and so designing the valve member that maximumlight will be passed through the valve gate l5 twice during eachcomplete oscillation of the reed The valve members are l3 and thevariation in intensity will follow the sine wave pattern.

} The valve member 23 is designed to cause a suitable pattern of thelight for the third partial of the note. The contour of this valvemember may be readily drawn following the same principractice.

then only the fundamental and therefore the corple as in designing thevalve member 25 but the shape should be such as to permit maximum lightto be passed through the light gate l5 three times during each completeoscillation of the reed. As shown, this valve member is formed with anarrow section 21, above its center, but so positioned that duringoscillation of the reed the larger portion 28 of the valve member willshut off the light from passing through the light gate l5 between twosuccessive impulses of light as controlled by the section 21. The narrowportion 29 at the other end ofthe valve member permits a maximum oflight while the reed is at one extreme of its oscillating movement.There are, therefore, three impulses of light impinging upon thephotoelectric cell 1 during each complete oscillation of the reed. Itwill be understood that ordinarily, but not always, it is desirable thatthe fundamental of the note to be produced should be louder than theovertones and that the second partial should be about equal to thethird. As a convenient arrangement for providing the desired relativeintensities while retaining the possibility of further control byadjustment of the separate members of the light valve 9, the light gateH3 is so formed, as shown in Fig. 4, that the apertures 30, 3|, 32through which the light from the ports, respectively 20, 23, 22 passesare of widths proportional to the desired intensities of the respec tlvepartials. In order to make provision for voicing the instrument, thewidths of these apertures may be made adjustable, if desired, as byproviding slides 33, 34, 35 movable to partially close the respectiveapertures. By this means the relative intensities of the severalpartials for the fully open position of the light valve 9 can beadjusted as desired. While provision for further controllingtheapertures from the console could be provided this is not ordinarilydesirable.

In the operation of the instrument it is desirable that stopscontrolling the tone colors may be provided at the console in accordancewith usual If, for example, a flute note is desired responding lightadmitted through the port 2| will be required. In order to provide suchan arrangement whereby the valve members controlling the harmoniccontent of the note and controlling the respective overtones maybeoperated for all notes of the instrument on the one console stop, thecorresponding valve members are mechanically connected to be operated inunison. The valve members which control the fundamentals and thosecontrolling the second and third partials are connected to threecorresponding mem- Figs. 8 and 9 obviously can be similarly conbers foroperation from theconsole. An illustrative arrangement isshown in Fig.6. As here indicated each valve member 2| controlling the fundamental isconnected by an operating arm 36 to an operating rod 31. Similarly thevalve members 23 are connected by arms 38 to operating rod 39 and valvemembers 25 are connected by arms 4|] to operating rod 4|. In this waywhen the corresponding stop is drawn at the console all of the valvemembers controlling the particular harmonic are operated in unison. Thelight controlling shutters 25' of the arrangement shown in nected.

Console stops similar to the spot tablets or knobs of modern pipe organsmay be arranged to ranged to control separately different sections sothat, for example, the notes of the low keys can be given a flutequality while the notes of the higher keys are given a differentquality.

Any suitable mechanism may be employed for actuating the operating rods.In Fig. 6 an electrical device is illustrated wherein an electric rotorsuch as a Selden motor or the like is gearconnected to each of theoperating rods 31, 39 and 4| to control the same. When the instrument isin operation the rotor element is energized to positively control theposition of each control rod. As shown, the rotor has six poles any pairof which may be energized to bring the armature to the correspondingposition. For example, when the opposite poles 45 and 46 are energizedthe rotor 41 will be drawn to the position indicated in Fig. 6. If it isdesirable to move the rotor to an intermediate position between twopairs of poles two adjacent pairs of poles may be both energized tocause the rotor to be moved to and held in an intermediate position.This expedient may be carried further to the extent of magnetizing oneset of poles with a greater magnetomotive force than the other.

In the arrangement illustrated in Fig. 1 and above described provisionis made for controlling only the fundamental, the second and the thirdpartials. In a larger instrument it is preferable to provide for controlof the fourth, fifth and even higher harmonics as well as those alreadymentioned. For such purpose there are certain advantages in thearrangement illustrated in Fig. 5 in which two reeds are employed foreach note. As shown, two reeds 50, 5| are provided and suction ismaintained in the chamber 52 in which these reeds are mounted. Upondepressing of the console key 53, controlling the particular note, bothgas filled lamps 54, 55 are illuminated, condensers, light valves,lenses, the mirror surfaced reeds and light gates being provided tocontrol the light beam passing to the photo-electric cell 56 as in thearrangement shown in Fig. 1. The light beams are periodically sweptacross the apertures of the light gates by the mirror surfaces of thevibrating reeds 50, 5|. Through this method of using more than one reedor each note. the crowding of the controlling valve members andsimplification of the mechanism can be obtained. Furthermore, the use ofoptical wedges, mirrors and other optical devices for bending light fromthe sides of the light valve can be avoided.

It is important that the reeds 50 and 5| should vibrate at exactly thesame frequency or at harmonic frequencies in order that all harmonicsproduced should be exact multiples of the fundamental. The advantages ofreeds vibrating at the same frequency probably equal the advantages, ofusing reeds of two harmonic frequencies and that arrangement is adoptedherein. If the reeds do not vibrate exactly in harmonic relation therewill be a. beating effect between the harmonics which will be more orless unsatisfactory musically. To this end it is preferable to soarrange one mod on the wind chest 52 that it will be it shall be causedto vibrate at its own natural period. This can be accomplished, forexample, by bending the reed slightly into the wind chamber or by otherexpedients. The natural frequency of the driven reed then enters only asaffecting theamplitude of vibration which will be greater as the naturalfrequency approaches that of the driving reed. By making use of thisresonance phenomenon the driven reed may be caused to vibrate at nearlyas great an amplitude as the driving reed.

It will be noted that in the arrangements of Figs. 1 and 5 thephoto-electric cells are each activated by light from two lamps. Thesecells operate satisfactorily if the light from other lamps is alsosuperimposed for which reason it is possible to so arrange the apparatusthat each photoelectric cell serves for several notes and the totalnumber of cells is correspondingly reduced. An arrangement is indicatedin Fig. 7 which makes this possible wherein the three units 60, G I, 62are positioned at such angles that the light from all impinges upon thecells 63 and 64. It will be noted that the feature shown in Fig. 13 forapplication to a multiple manual instrument is incorporated in thisarrangement,

. Amplfficatiou .--Any suitable amplifying arrangement may be used. InFig. 10 is indicated an illustrative circuit. The number ofphotoelectric cells employed will depend upon the de sign of theinstrument but the three shown will sufficiently illustrate theamplifying circuit. One pick-up amplifier may be associated with eachcell or as many as twenty cells may be electrically connected inparallel or otherwise associated to feed into a single pick-upamplifier. It is also to be understood various mirror reflecting schemesmay be employed to reduce the number of photo-cells required byreflecting a large number of light beams into one or more cells ofsuitable size. Referring to Fig. 10 each photo-electric cell 1 of theseries is associated with a vacuum tube amplifier 65 of conventionaldesign and each amplifler is provided with a suitable gain control 66.The outputs of amplifiers 65 are fed into transformers 61 whosesecondaries are connected to tube matching resistances 6B. Theseresistances are connected in series and connected to the primary oftransformer 69 whose secondary is'conoperate loudspeaker 15 at asuitable musical sound level. It will be understood by those skilled inthe radio and broadcasting arts that amplifiers 65 and the connectionsto the transformer 69 constitute merely an illustrative arrangement for'feeding the several currents into amplifier 10. 'In eneral, the acousticconditions andsize of audience will determine the size of the amplifierl0 and acoustic translating equipment 15.

It has been found that there are certain advantages in providing aplurality of separate amplifying and loud speaker systems for thedifferent sections of the organ. The base notes of the pedal sectionespecially in the case of an in strument to be used in a largeauditorium should he placed on one separate system and the outputcontrolled by each manual may advantageously be on a separate system. Itis desirable to have separate amplification controls for each system.

Trem0lo.-In order to secure certain desirable forced to vibrate by thealternating pneumatic fluctuations in the wind chest rather than thatmusical effects it is preferable to provide a tremolo device. Perhapsthe simplest way to do this is to provide a tremolo in the wind supplyof the beater type long familiar to pipe-organ practice. Such a deviceis indicated at 76 in Fig. 1. Other electrical methods are possible,such as varying the exciter lamp voltages at the rate desired for thetremolo to be produced. A variable resistance 1'! controlled by a crank'18 is indicated in the light circuits of Fig. l to illustrate thisarrangement. Alternatively a moving light shutter 79 Fig. 15 may be usedperiodically to change the illumination to give an intensity tremolo.The above mentioned beater tremolo will cause a small frequency tremoloin addition to the intensity tremolo.

Percussion tone.-Another important musical effect is that of thepercussion tone. There are several methods of producing this effect. The

method preferred for the instrument illustrated I consists in providinga time delay relay associated with each note as indicated in theelectrical diagram Fig. 11. When the console key 80 is depressed lamp BIis illuminated through the circuit shown by the current from the source82.

Normally the switch 83 is closedcausing series resistance 84 to be shortcircuited. Immediately after the console key is depressed therefore thelamp 8t attains maximum illumination. Shortly thereafter (the timeinterval depending upon the 1 design of the time relay 85), the timedelay relay opens the switch 83 and the resistance 84 is introduced intothe lamp circuit. The voltage therefore is decreased because of theadded series resistance 84. This change in illumination causes differentperiod of delay.

The percussion tone may be obtained by other devices which reduce theintensity of the note after it is initiated as, for example, byproviding a slow acting shutter in the light beam. Such a shutter isindicated at B6 in Fig. 5 and can be made to operate slowly byassociating it with the armature of a slow acting electrical orpneumatic relay 81. bodiment of the invention affects only the lightinitiating the fundamental or the fundamental and part of the overtonesgiving a desirable effect.

Volume control-Volume control, which is of great importance musically,may be obtained in a number of ways. The method or methods which willgive the most satisfactory results will depend upon the size andarrangement of the particular instrument under consideration. For

the one manual instrument, the output of the power amplifier may bevaried by a control H associated with a console foot pedal 12 similar tothe swell shutters foot control on a pipe organ console. Alternativelyor additionally, a console pedal controlled resistance 93 (Fig. 1) maybe introduced in series with the exciting lamps, the latter always beingin parallel with each other. This method has several disadvantages andsome special advantages. The one serious disadvantags is that the lampshave an undesirably long of such a series resistance is that the seriesre- This shutter when applied in this emsistance has a variable voltagedrop across it depending upon the number of lamps that are excited. Thisresults in causing the introduction of additional lamps to affect theillumination of the other lamps already excited. To illustrate, if

two console keys are depressed andthen a third is depressed, theaddition of this third note would cause the other two'notes to becomeweakened.

This would give a new musical effect which, how-;

ever interesting for special purposes, is not suited for a generalvolume control. This disadvantage so'far as a'true volume control isconcerned may beovercome bymaintaining all the excited lamps in acontinuously illuminated state with said variable' series resistanceassociated. therewith and .keying the light beams by meansofquick-acting have at least one complete set of reeds associated witheach manual. For certain celeste and en'- semble effects I prefer to usemore'than one set of reeds per manual. See Fig. 5 and the descriptionthereof. n the other hand, one set of reeds may be used for more thanone manual by associating more than one light source with each reed.Such an arrangement is indicated in Fig. 14,

wherein light from two lamps '92 is reflected by the mirror'surface ofreed 93 to cells 94.

For the two manual instrument, I may have tworeeds associated with thesame musical pitch mounted in the same wind channel, for example asshown at-95 in Fig. 13. When so mounted, the two reeds may be made tovibrate at exactly the same frequency. It will be apparent that two setsof photo-cells 90 may be arranged to pick up the light beams associatedwith the respective manuals. A general volume control can be chtained bythe manipulation of the final amplifier output as in the case of the onemanual instrument. It is also desirable to have individual dynamiccontrol over the output for each manual. For this purpose the two seriesof similar photoelectric cells will deliver their output throughseparately controllable amplifying devlces wherei by the relativeintensity of the outputs of the two manuals can-be controlledindependently applying the principles embodied-in the arrangementillustrated in Fig. 10. Obviously the .quality of the output initiatedby the different manuals can also be controlled independently bysuitableadjustment of the light valves of the respective light sources. Theparticular arrangement of loud speaker shown is illustrative and notintended as excluding the use of other arrangements.

It will be noted furthermore that the arrange-- ments indicatedin Fig.13 and Fig. 14 are adapted to be applied in combination with thearrangement of light sources, reeds and photo-electric cells indicatedin Fig. 1 or 5.

Another method forobtaining control over the output of the two manualsis to have all the exciter lamps continuously illuminated and keyingaccomplished through the aid bf quick-acting shutters while a. seriesresistance under control of a. foot pedal is associated with the lampfor each manual. Such an arrangement is] indi-. cated in Fig. 15 whereina shutter 91 keys the note and resistance 00 controls the intensity.

An alternative method for obtaining individ ual manual dynamic -control,which has some advantages, involves the use of devices operated so as todiminish the light available for exciting the photo-cell. To this end, Imay provide an optical wedge or a film of varying density associatedwith each note, and connect all the optical wedges or films for a singlemanual to one operating rod; This rod may be moved in any suitable-way.These optical wedges or films can be situated at any point along theoptical system. I prefer to situate them between the harmoniccontrolling light valves and the mirror surfaced reeds as indicated atI0 in Fig. 1. The voltages applied to the exciter lamps is alwayssubstantially the same and keying is accomplished by flashing theexciter lamps.

It will be noted that the light passing the light gate may be consideredas one beam having a complex pattern or as three separate beams.

Amplifier bZocking..In order to avoid a noticeable photo-cell hiss andother stray noises in the output of the instrument it is desirable toprovide a means for automaticblocking of the amplifier when no signal isapplied. When no console keys are depressed, the instrument should be asquiet as possible. Unless some blocking arrangement is provided, theinherent photo-cell hiss and other stray pickup will be unpleasantlydiscernible during the silent portions of a musical rendition. When anote is being played the photo-cell hiss, etc. will be largely masked.During such times the blocking of the amplifier will be removed and itwill the case of any amplifier. The grid of tube IN is biased to itsnormal value with battery I02. It will be seen that in series with thisgrid bat- ,tery to ground is a variable resistor I03. When a directcurrent flows through this resistance, there will be a direct voltagedrop across it. This voltage will be added in proper algebraic sense tothat of the normal bias battery I02. The operation of the circuit issuch, that when no signal is applied, a current will be flowing throughresistance I03 and thus the extra bias to the grid is adjusted by makingresistance I03 the proper value, and it is of such a value that the gridof tube IOI becomes biased to cut-off when a current fiows through saidresistance. Under such circumstances, tube IOI becomes inoperative andeffectively blocks inherent photo-electric cell hiss and other straypick-up. It will be seen that the secondary of transformer I00 feedsalso to the grid of tube I05 through blocking condenser I00 andadjustable resistance H3 which condenser is introduced to block anydirect current from affecting the potential ofthe grid of tube I05. TubeI05 is biased normally with battery I01 through resistance 3 and itsoperation is always that of a simple amplifier. The output of tube I05is fed into transformer I08 which is supplied with a center-tappedsecondary. This secondary feeds as a full-wave rectifier into two of theplates of tube I09 which is, inefl'ect, a combination of two diode andone triode elements. Parallel elements H0 and III constitute a load onthis full-wave rectifier. When the primary of transformer I08 isenergized, there will be a voltage induced in the sec-- qondary, and thegrid of ti'ibe I09 will be at a negative potential due to the full-waverectifier acsystem to become operative.

tion. This means that electrons emitted from the cathode of tube I09will be blocked by the negatively charged grid of tube I09. The resultis that the plate current will be zero and consequently no voltage dropwill appear across resistance I03. This leaves the bias on tube IOI atits normal value, and said tube operates as i an amplifier deliveringits output to transformer I04 whose secondary feeds to the poweramplifier and loud speakers. This situation exists when a signal isapplied. Grid potentiometer H3 is made adjustable in order that theinherent photo-cell hiss will not of itself cause the The minimum signalintensity as compared with the noise level will determine the positionof slider M4 on potentiometer resistance II3. Considering now the casewhere no signal is applied, there will be no voltage across thesecondary of transformer I08. Consequently, there will be no rectifyingaction of tube I09, and the center-tap of transformer I08 and the gridof tube I09 will be at zero potential. At zero grid potential, theelectron flow from the cathode of tube I09 will not be impeded, and acathode to plate electron current will flow. Battery H2 supplies thenecessary positive plate potential for tube I09. Under thesecircumstances a current will flow through resistance I03, and a voltagedrop will appear across said resistance. This extra voltage drop causesthe grid bias of tube IOI to rise to cut-oil thus making the tubeinoperative. Thus, no inherent noise, etc. pass tube IIlI when no signalis applied. The values of resistance H0 and capacitance III willdetermine the time delay in blocking tube I 0|. That is, the charge oncondenser III will take a finite time to leak 01f through resistance H0.Also, as the grid of tube I09 is connected to said condenser itspotential will drop in said finite time. The length of this period isdetermined by the value of capacitance III and resistance IIO. Thepresence of this time delay combination is made preferable because thecircuit as a whole is not instantaneous in operation when a signal isapplied-there is a slight delay. To overcome this difiiculty, I includethis time delay element. Musically, this means that swift movingpassages may beplayed without having tube I OI blocked between each noteof said swift moving musical passages.

For very high notes the reeds are short and relatively difiicult to tuneand pipes or reeds of the usual type commonly used in pipe organs aresmall requiring relatively little space. Accordingly, it is practicableto use for the'upper notes a unit having such pipes or reeds enclosed ina sound proof box. The output of these pipes or reeds may be picked upby a suitable microphone and superimposed upon the output of thephotoelectric unit or it may be delivered to a separate loud speakerthrough a suitable amplitude control.

Obviously various modifications of the arrangements illustrated may bemade such as providing other arrangements for keying as by means ofsetting the reeds in vibration individually as is common practice inordinary reed or pipe organs. This would eliminate certain noises. Alsothe manner of controlling the light in response to the movement of thereeds may be varied as convenience may require. For example, it ispossible to vary the amount of light as the reed vibrates by anarrangement wherein the light passes the end of the reed and thevibrating reeds act as a light valve opening and closing the lightaperture.

The tuning of the reeds may be accomplished in various ways includingfiling as is common practice or by varying the air pressure as by valvesII5, Fig. 1, or by other known expedients.

Instead of using merely one or two reeds to produce the whole content ofeach note, the arrangement may be such that each partial of the note isproduced under control of a separate reed. To accomplish this anarrangement embodying certain principles of my prior Patent No.1,901,985 may be adopted. Such an arrangement is illustrated in Fig. 16wherein is shown a circuit providing that each note as produced mayconsist of a fundamental and three overtones. As herein illustrated theintensity of the overtones and fundamental may be varied relative toeach other to provide the desired quality of the notes. In each case theovertones are obtained from the corresponding units of the higher (orlower) notes of the instrument.

In the diagram incandescent lamps I2I to I 21 may be those lampsassociated with reeds of pitches corresponding to the C keys on theinstrument or to the keys of notes harmonically related to each other.These keys and lamps are associated with key switches I3I to I31respectively. Each key switch is a gang switch arranged to close thecircuit of the lamp corresponding to the key and also the desired lampscorresponding to higher or lower C notes or other partials to give thedesired harmonic content. cuit connections between each switch and thelamps are similar, each switch except at the ends of the series beingshown as arrangedto close exciting circuit for a lamp corresponding tothe fundamental of the note, a second lamp corresponding to asub-harmonic and two lamps corresponding to upper harmonics. Forexample, switch I32 may close a circuit to lamp I22 and also to lampsI2l, I23 and I24. In the circuits for each key switches and resistancesare introduced to provide complete control of the harmonic content fromthe console. Switches I40, which may be connected to form a gang switchcontrolled from the console, may be closed or opened to provide or omitthe subharmonic coupling and variable resistances I4I may be adjusted,also by gang control, to determine the intensity. Switches I42 andvariable resistances I43 similarly make possible the control of thefundamental and switches I44 and I46 with resistances I45 and I4! servethe same purpose for the upper harmonics.

It will be understood that if the instrument is tuned according to theeven-tempered scale, it is impossible to select notes from said scalewhich wil be exact odd harmonics of a fundamental 01 a note of saideven-tempered scale. However, they may be approximated quite closelywith notes selected from the even-tempered scale and the odd harmonicpitches obtained in this way are suitable musically for many purposes.

I claim 1. A musical instrument comprising, in combination, a series ofkeys, light sensitive cells. a series of vibratory elements, meanscontrolled by said keys and vibratory elements for causing light of anintensity varying under the influence of said vibratory elements toimpinge upon said light sensitive cells and means for amplifying theoutput of said light sensitive cells.

2.. A musical instrument comprising, in combination, a light sensitivecell, a source of light The cirlight beam comprises a film-of densityvaryi" operable to cause light to impinge upon said cell, a vibratoryelement, means whereby the intensity of the light impinging upon saidlight sensitive cell is caused to vary under control of said vibratoryelement, means for converting the output of the light sensitive cellinto sound and keying means operable to control the inception andtermination of the sound.

3. In a musical instrument, in combination, a light sensitive electricalcell, an amplifier arranged to receive the output thereof, a lightsource arranged to direct a beam of light onto said light sensitivecell, and a vibratory reed in the path of light between the light sourceand the light sensitive cell for varying the light intensity at the cellin accordance with a pattern approximating a sine wave pattern of audiofrequency.

4. In a musical instrument, in combination, a light sensitive electricalcell, an amplifier arranged to receive the output thereof, a lightsource arranged to direct a beam of light onto said light sensitivecell, and means in the path of light between the light source and thelight sensitive cell for varying the light intensity at the cell tocorrespond to the harmonic composition of a note to be producedcomprising a vibratory element and means cooperating therewith to causea variation in intensity at a rate difiering from the rate of vibrationby a predetermined factor.

5. In a musical instrument, in combination, a light sensitive electricalcell, an amplifier arranged to receive the output thereof, a lightsource arranged to direct a beam-of light onto said light sensitivecell, and means in the path of light between the light source and thelight sensitive cell for varying the light intensity at the cell tocorrespond to the harmonic composition of a note to be producedcomprising a plurality of vibratory elements and means cooperatingtherewith to cause a variation in intensity at rates controlled by therates of vibration;

6. In a musical instrument, in combination, a light sensitive electricalcell, an amplifier arranged to receive the output thereof, a lightsource arranged to difect a beam of light onto said light sensitivecell, means in the path of light between the light source and the lightsensitive cell for giving a pattern to the light beam, a vibratoryelement and a mirror actuated by the vibratory element and operativeduring oscillation to transmit to the light sensitive cell difierentportions of the light beam to thereby deliver to the cell light varyingin intensity in accordance with the harmonic composition of a note to beproduced.

'7. A musical instrument as defined in claim 6, wherein the means forgiving a pattern to the light beam comprises a lightgate and devicesadjustable therein for giving difierent patterns to the beam.

8. A musical instrument as defined in claim 6, wherein themeans forgiving a pattern t"-';; i;the

in accordance with the patternto be given to the light beam and meansfor varying the amount of light is provided.

9. In a musical instrument, in combination, a

- light sensitive electrical cell and an amplifier arranged to receivethe output thereof, means for directing a beam of light onto said cell,means for periodically varying the intensity of the light at said cellincluding a vibratory reed and means for maintaining said reed in astate of vibration,

' directing a beam of light onto said cell, means for periodicallyvarying the intensity of the light at said cell including a reed andpneumatic means for vibrating said reed at its natural frequency, andkeying means for controlling the illumination from said lamp.

\ 11. In a musical instrument, in combination, a light sensitiveelectrical cell and an amplifier arranged to receive the output thereof,means for directing a plurality of beams of light onto said cell andvibratory reeds for varying the intensities of said beams of light atfrequencies corresponding to the frequencies of difierent par- -tials ofa note to be produced.

12. In a musical instrument, in combination, a light sensitiveelectrical cell and an amplifier arranged to receive the output thereof,means for directing a plurality of beams of light onto said cell andvibratory reeds for varying the intensities of said beams of light atfrequencies corresponding to the frequencies of different notes to andmeans cooperating with said reeds for varying the light intensities ofrespective beams of light to correspond to the frequencies of differentpartials of the note to be produced.

, 14. In a musical instrument, in combination, a series of lightsensitive cells, a series of light sources arranged to direct beams oflight to said cells, keying means for controlling the light sourcesindividually at the will of the operator, a series of .vibratory reedsarranged in the paths of the beams of light operative to vary the lightintensityas transmitted to the light sensitive cells to correspond tothe patterns of the several notes to be produced.

15. Amusical instrument as defined in claim 3, wherein a variableresistance is interposed in the light circuit and means for varying theresistance in accordance with a predetermined pattern is provided.

16. A musical instrument comprising, in combination, a light sensitivecell, a source of light, means for forming a light beam, means forvibrating said light beam transversely, a light valve in the path ofsaid light beam arranged to cause variation of the intensity of the beamas passed through the valve in accordance with the rate of vibration ofthe light beam.

17. A musical instrument comprising, in combination, a light sensitivecell, a source of light, means for forming a light beam, means forvibrating said light beam transversely, a light valve in the path ofsaid' light beam, said light valve comprising sections extendingtransversely oi the light beam in the direction of its vibratorymovement and varying in density substantially in RICHARD HOW RANGER.

